1. Field of the Invention
The present invention relates to the field of vehicle maintenance, and more specifically, to servicing automatic transmission subsystems.
2. Background
Automatic transmissions frequently require servicing such as replacing used fluid with fresh fluid in order to properly maintain them and extend the life of the component and associated vehicle. Early attempts at developing automatic transmission fluid transfer machines often resulted in relatively lengthy and complicated procedures. Many of these devices relied upon compressed gases to circulate the fluid and thus required some sort of compressed air source adding to the device's complexity. Such early attempts also required significant manual operation and supervision as the operator had to continually monitor gauges and other instruments to monitor the fluid flow to achieve the desired performance.
While some of these devices proved satisfactory for their time, the next level of automatic transmission fluid transfer machines introduced a degree of automation to the fluid exchange process thus reducing the extent of operator intervention. However, the plumbing proposed in an effort to automate the process and perform the steps typically associated with a complete automatic transmission fluid service, typically employed a relatively large number of plumbing components such as multiple dedicated pumps, gauges, and several valves. While many of these devices have also proven satisfactory in their performance there remains a push for reducing the number of components, cost of manufacture, and reduced assembly time while maintaining the capability to perform the desired procedures.
Efforts to resolve this long standing problem led to the introduction of a number of devices of the single pump variety. Some examples of these single pump devices can be found in U.S. Pat. Nos. 5,482,062 and 5,337,708 to Chen; U.S. Pat. No. 5,447,184 to Betancourt; U.S. Pat. No. 5,472,064 to Viken; U.S. Pat. No. 6,035,903 to Few, owned by assignee of this application; and Japanese Unexamined Patent Application No. 2-72299. It is clear from a review of the devices shown in these patents that, while success was achieved in reducing some number of components, such as the pumps, it was necessary to increase the remaining plumbing in order to perform the necessary fluid transfer processes such as complete fluid exchange, recirculation, and draining both used and new fluid tanks or such desired processes could not performed using a single pump. Frequently a separate drain pump or a more complicated and costly reversible pump has been incorporated to perform the desired fluid servicing tasks. While some of these devices, such as that described in U.S. Pat. No. 6,035,903, have proven satisfactory in the field, there remains the ever present need to develop a fluid changing apparatus with a minimal number of components to reduce costs, maintenance, and assembly time, yet still perform the fluid servicing procedures associated with an automatic transmission service.
What is needed is a fluid changing apparatus configured to conveniently address the needs of the fluid change operator using a single pump configuration integrated into a relatively minimal component fluid transfer system, something the previous attempts have failed to achieve up to this time.